Picture frame



FIG. 1 is a front elevational view of a picture frame showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a left end elevational view thereof;

FIG. 5 is a right end elevational view thereof; and

FIG. 6 is a rear elevational view thereof. 

The ornamental design for a picture frame, as shown. 